Caustics Generation by using Photon Mapping

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Caustics Generation by using Photon Mapping

• Presentation by Michael Kaiser and Christian
  Finger
• Advised by Dr. Marcus Magnor
• 13.02.2004
• Light and Color in Nature Seminar,
• Max-Planck-Institut für Informatik

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Motivation

• Create nice pictures with translucent objects and
  rendering nice effects on diffuse surfaces.

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Overview

• Caustics
• Photon Mapping
• Results

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Light Transport Notation

• L Lightsource
• E Eye
• S Specular reflection
• D Diffuse reflection
• (k) one or more k events
• (k) zero or more of k events
• (k)? zero or one k event
• (kk) a k or k event

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Caustics

• Caustics are formed when light reflected from or
  transmitted through one or more specular surfaces
  strikes a diffuse surface.
• In Light transport notation LSDE

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Comparisons

• Classical Ray Tracing
• LD?SE
• Does not support Caustics.
• Path Tracing
• L(SD)E
• Would be qualified for simulating caustics.
• But Probability of going through a series of
  LSDE is small.
• Bidirectional Path Tracing
• L(SD)E
• Would be also qualified for simulating
  caustics.
• Produces correct pictures, unbiased solution.
• Takes too much time for same quality as photon
  mapping.

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Comparisons

• Radiosity
• Handles only diffuse reflections LDE.
• Not suitable for rendering caustics.
• Photon Mapping
• Handles all kinds of reflections.
• It has the following possibilities L(SD)D
• Good for Caustics.

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2-Pass Algorithm

• First Pass
• Generating a Global Photon Map and Caustic Map.

• Second Pass
• Rendering the Photon Map via Distribution Ray
  Tracing.

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Photon Maps

• Global Photon Map
• All Photons with property L(SD)D are stored.
• Caustic Map
• Only Photons with paths LSD are directly stored.
• Application of a projection map.

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Photon Mapping

• Rendering equation is solved by a photon map.
• Density estimation

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Photon Mapping

• For the rendering part incoming radiance is
  divided into four parts

Specular Illumination
Caustic Illumination
Direct Illumination
Diffuse Indirect Illumination
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Photon Mapping


Direct Illumination
Indirect Illumination


Specular Part
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Photon Mapping

Caustics

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Results
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Results
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Results
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Outlook

• Rendering participating media
• Additional Volume Photon Map.
• Rendering Volume Caustics.

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Literature

• Henrik Wann Jensen, Realistic Image Synthesis
  Using Photon Mapping, A.K. Peters, 2001

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• Questions?